feat: delete instance docs

frontends/lander/content/docs/usage/delete.md

@@ -0,0 +1,17 @@
+---
+title: Delete Instance
+category: usage
+description: Instances, including their subdomain and all the local data (not S3), can be deleted.
+---
+
+Delete Instance will delete your instance and data immediately.
+
+To delete an instance, you must be in [Maintenance Mode](/docs/usage/maintenance) first, and the running status of your instance must be `Idle`.
+
+Deleting your instance will immediately and permanently delete your instance:
+
+- Your subdomain
+- `pb_data/*`
+- `pb_public/*`
+- `pb_migrations/*`
+- `pb_static/*`